Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02921179 2016-02-19
SPECIFICATION
Docket No. 26172.010
TO ALL WHOM IT MAY CONCERN:
BE IT KNOWN that we, Garrett S. Boyd and Mitchell A. Boyd, citizens of the
United
States of America, residing in the State of Texas, have invented new and
useful improvements in
a
IMPROVED CLUTCH ASSEMBLY FOR BYPASS PLUNGERS
of which the following is a Specification:
1
1 BACKGROUND OF THE INVENTION
2
3 1. Field of the Invention:
4
The present invention generally relates to gas lift devices for rejuvenating
low-producing
6 or non-productive oil or gas wells, and more particularly to improvements
in the design and
7 construction of bypass plungers.
8
9 2. Background of the Invention and Description of the Prior Art:
11 A conventional bypass plunger is a device that is configured to freely
descend and ascend
12 within a well tubing, typically to restore production to a well having
insufficient pressure to lift
13 the fluids to the surface. It may include a self-contained valve - also
called a "dart" or a "dart
14 valve" in some embodiments - to control the descent and ascent Typically
the valve is opened
to permit fluids in the well to flow through the valve and passages in the
plunger body as the
16 plunger descends through the well. Upon reaching the bottom of the well,
the valve is closed,
17 converting the plunger into a piston by blocking the passages that allow
fluids to flow through the
18 plunger. With the plunger converted to a piston, blocking the upward
flow of fluids or gas, the
19 residual pressures in the well increase enough to lift the plunger and
the volume of fluid above it
toward the surface. Upon reaching the surface, the fluid is passed through a
conduit for
21
2
Date Recue/Date Received 2022-06-28
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, 1 recovery, the valve in the plunger is opened by a striker mechanism,
and the plunger descends to
2 repeat the cycle.
3
4
In a typical bypass plunger the valve is similar to a poppet valve, with
a valve head
attached to one end of a valve stem, such as an intake valve of an internal
combustion engine.
6 The valve head, at the inward end of the stem, may be configured to
contact a valve seat within
7 the hollow body of the plunger. The stem protrudes outward of the bottom
end of the plunger
8 body. A clutch device may surround the stem of the valve to retard and
control the motion of the
9 stem and thereby maintain the valve in an open or closed configuration
during respectively the
descent or ascent of the plunger. The valve thus moves between these two
positions to open the
11 flow passages at the surface when the plunger contacts the striker
mechanism, and to close the
12 bypass passages at the bottom of the well when the stem strikes the
bottom, usually at a bumper
13 device positioned at the bottom of the well. Descent of the plunger is
controlled by gravity,
14 which pulls it toward the bottom of the well when the valve is open.
16
This valve or "dart" may be held open or closed by the clutch ¨ typically
a device that
17 exerts circumferential friction around the valve stem. The dart may be
held within a hollow cage
18 attached to the plunger by a threaded retainer or end nut at the lower
end of the plunger
19 assembly. Thus, the valve reciprocates between an internal valve seat
(valve closed) in a hollow
space inside the cage and the inside surface of the lower end of the cage
(valve open). A
21 conventional clutch is appropriate for some applications, especially
when its assembly is well
22 controlled to produce unifoi
________________________________________________ in assemblies. Such a clutch
may be formed of a bobbin split into
23 two hemispherical halves and surrounded by one or two ordinary coil
springs that function as a
24 sort of garter to clamp the stem of the valve or dart between the two
halves of the bobbin,
thereby resisting the sliding motion of the stem within the bobbin. The clutch
assembly is
26 typically held in a fixed position within the cage. Each 'garter' spring
is wrapped around its
27 groove and the ends crimped together, typically in a hand operation that
is subject to some
28 variability in the tension around the bobbin halves and possible failure
of the crimped joint,
29 which could affect the reliability of the clutch when in a downhole
environment.
3
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1
2 While generally effective in lifting accumulated fluids and gas of
unproductive wells
3 such conventional bypass plungers tend to be complex and suffer from
reliability problems in an
4 environment that subjects them to high impact forces, very caustic
fluids, elevated temperatures
and the like. Various ways have been attempted to simplify construction of
bypass plungers,
6 improve their reliability and performance, and to reduce the cost of
manufacture. However,
7 failures remain common, and a substantial need exists to eliminate the
causes of these failures.
8 What is needed is a bypass plunger design that solves the structural
problems with existing
9 designs and provides a more reliable and efficient performance in the
downhole environment.
4
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1 SUMMARY OF THE INVENTION
2
3
Accordingly there is provided a bypass plunger comprising a unitary hollow
plunger
4
body and valve cage formed in one piece having first and second ends, the
valve cage formed at
the second end, and the valve cage having internal threads at its distal end
for receiving a
6
retaining nut having external threads at one end thereof; a poppet valve
having a valve head
7
connected to a valve stem, the poppet valve reciprocatingly disposed
within the valve cage such
8
that the valve head is oriented toward a valve seat formed within the
hollow body; a retaining nut
9
having external threads formed in the outer surface thereof and
corresponding to internal threads
formed in the distal end of the valve cage to retain the poppet valve within
the valve cage; and at
11
least one helical groove formed for at least one-half revolution around
the outer surface of the
12
hollow plunger body for a portion of the length of the hollow body
approximately midway
13 between the first and second ends.
14
In another embodiment, there is provided a bypass plunger comprising a unitary
hollow
16
plunger body and cage, the valve cage formed at a lower end thereof and
configured with
17
internal threads at its lower end for receiving a retaining nut having
external threads at one end
18
thereof; a poppet valve having a valve head connected to a valve stem and
reciprocatingly
19
disposed within the valve cage; and a retaining nut having external
threads for closing the lower
end of the valve cage to retain the poppet valve within the valve cage; and at
least two crimples
21 to lock the retaining nut to the valve cage.
22
23
In another embodiment there is provided a bypass plunger comprising a
unitary hollow
24
plunger body and valve cage, the valve cage formed at a lower end thereof
and configured with
internal threads at its lower end for receiving a retaining nut having
external threads at one end
26
thereof; a poppet valve having a valve head connected to a valve stem and
reciprocatingly
27
disposed within the valve cage; a retaining nut having external threads
for closing the lower end
28
of the valve cage to retain the poppet valve within the valve cage; a
continuous helical groove
29
machined into a central portion of the hollow body midway between upper
and lower ends
5
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1 thereof and having a predetermined pitch, depth, and profile according to
required spin and rate
2 of descent of the bypass plunger through a well tubing; first and second
crimple detents
3 extending inward from the surface of the valve cage at the second end of
hollow body and along
4 first and second opposite radii of the valve cage into corresponding
relieved spaces in the
proximate external threads foinied in the outer surface of the retaining nut;
and a canted coil
6 spring disposed within a circumferential groove formed into the inside
wall of the retaining nut
7 such that the canted coil spring exerts a substantial radial clamping
force on the stem of the
8 poppet valve, thereby forming a clutch to retard the motion of the poppet
valve between open
9 and closed positions.
11 Accordingly there is provided a clutch assembly for a bypass plunger
having a valve cage
12 and a reciprocating dart valve, the dart valve having a round stem and
disposed within the valve
13 cage, the clutch assembly comprising: a partition nut, threadably
installed within an internal
14 thread of an open end of the valve cage following installation of the
dart valve in the valve cage;
a split bobbin assembly having first and second hemispherical halves, each
half of the split
16 bobbin assembly having formed there around at least one circumferential
groove, and the
17 assembly installed on the stem of the dart valve; a coil spring disposed
in each circumferential
18 groove to secure the split bobbin assembly around a stem of the dart
valve, thereby forming the
19 clutch assembly; a retaining nut threadably installed within the
internal thread of the valve cage
following installation of the clutch assembly within the valve cage; and at
least first and second
21 crimples formed into the outer surface of the valve cage and extending
into relieved spaces
22 formed in an external thread foi Hied on each one of the retaining
nut and the partition nut.
23
24 In another embodiment there is provided a clutch for a bypass plunger
having a
reciprocating valve, comprising a clutch body formed as a circular split
bobbin assembly having
26 first and second halves, the assembly defined by a central axis, an
inside radius, an outside
27 radius, and first and second opposite faces normal to the central axis;
a circumferential groove
28 disposed in the surface defined by the outside radius of the split
bobbin assembly; and a canted-
6
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1 coil spring disposed in the circumferential groove to secure the split
bobbin assembly around a
2 valve stem.
3
4
Accordingly there is provided a dart valve for a bypass plunger, the dart
valve disposed to
move reciprocatingly within a valve cage of the bypass plunger between seated
and unseated
6 positions and constrained by a clutch mechanism within the valve cage or
its retaining nut,
7 comprising a poppet valve comprising a valve stem and a valve head; a
valve head connected to
8 one end of the valve stem, the valve head including a sealing face to
make sealing contact with a
9 valve seat within the bypass plunger; and the valve stem includes a
predetermined surface
profile for moderating tension produced by the clutch mechanism during the
reciprocating
11 motion of the poppet valve.
12
13
In another embodiment there is provided an improved valve dart assembly
for a one-
14 piece hollow plunger body and valve cage of a bypass plunger, the valve
cage formed at a lower
end of the hollow plunger body and configured with internal threads at its
open lower end, the
16 improvement comprising a poppet valve having a valve head connected to a
valve stem and
17 reciprocatingly disposed within the valve cage; a retaining nut having
external threads at one end
18 thereof for engaging internal threads foi
__________________________________ riied in the open lower end of the valve
cage to retain the
19 poppet valve within the valve cage; and a canted coil spring disposed
within a circumferential
groove formed into the inside wall of the retaining nut such that the canted
coil spring exerts a
21 substantial radial clamping force on the stem of the poppet valve,
thereby forming a clutch to
22 retard the motion of the poppet valve between open and closed positions.
23
7
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1 BRIEF DESCRIPTION OF THE DRAWINGS
2
3 Figure 1 illustrates a side exploded view of one embodiment of a
bypass plunger
4 according to the present invention;
6 Figure 2 illustrates a cross section view of the embodiment of Figure
1 as assembled;
7
8 Figure 3 illustrates a cross section detail view of the lower end of
the embodiment of
9 Figure 2 with the valve shown in an open position;
11 Figure 4 illustrates a cross section detail view of the lower end of
the embodiment of
12 Figure 2 with the valve shown in a closed position;
13
14 Figure 5 illustrates a side cross section detail of an end
(retaining) nut and canted coil
spring for use with the embodiment of Figures 1 - 4;
16
17 Figure 6 illustrates an end cross section detail of the end
(retaining) nut and canted coil
18 spring depicted in Figure 5, for use with the embodiment of Figures 1 -
4;
19
Figure 7 illustrates an enlarged version of Figure 3;
21
22 Figure 8 illustrates an end cross section view of the embodiment
depicted in Figure 7;
23
24 Figure 9 illustrates a side view of a hollow body according to the
present invention
having a tight helix profile disposed in a central portion of the embodiment
of Figure 1;
26
27 Figure 10 illustrates a side view of a hollow body according to the
present invention
28 having an open helix profile disposed in a central portion of the
embodiment of Figure 1;
29
8
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1 Figure 11 illustrates a first example of an alternative embodiment of
a plunger valve
2 clutch according to the present invention;
3
4 Figure 12 illustrates a second example of an alternative embodiment
of a plunger valve
clutch according to the present invention;
6
7 Figure 13 illustrates a third example of an alternative embodiment of
a plunger valve
8 clutch according to the present invention;
9
Figure 14 illustrates an alternate embodiment of the bypass plunger of Figure
1 that uses
11 a split bobbin clutch;
12
13 Figure 15 illustrates a first example of an alternate embodiment of a
plunger valve dart
14 according to the present invention;
16 Figure 16 illustrates a second example of an alternate embodiment of
a plunger valve dart
17 according to the present invention;
18
19 Figure 17 illustrates a third example of an alternate embodiment of a
plunger valve dart
according to the present invention;
21
22 Figure 18 illustrates a detail view of the profile of a feature of
the embodiment of Figure
23 17;
24
Figure 19 illustrates a die for use in a press to form a crimple used in the
embodiments of
26 Figures 3, 4, 7, and 8;
27
28 Figure 20 illustrates an alternate embodiment to Figure 4, showing a
split bobbin clutch
29 assembly for a bypass plunger within a valve cage;
9
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_ 1 Figure 21 illustrates a cross section detail view of an
alternate embodiment of the lower
2 end of the embodiment of Figure 3 with the valve shown in an open
position; and
3
4 Figure 22 illustrates a cross section detail view of an
alternate embodiment of the lower
end of the embodiment of Figure 4 with the valve shown in a closed position.
6
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1 DETAILED DESCRIPTION OF THE INVENTION
2
3 In an advance in the state of the art, the novel bypass plunger described
herein with the aid of the
4 accompanying drawings yields improvements in a number of areas. The
result is a novel
combination of four essential features incorporated in a unibody bypass
plunger (aka unibody
6 gas lift plunger) as disclosed herein. The principle components of the
unibody bypass plunger
7 include the one-piece hollow plunger body and the integral valve cage
formed at its lower end.
8 The valve cage assembly includes a valve dart and a clutch mechanism
enclosed within the cage.
9 A retaining nut (or end nut) that retains the valve dart and clutch
mechanism within the cage
completes the valve dart cage assembly. The novel features of the present
invention provide
11 reduction of manufacturing costs, and enhanced performance, durability,
and reliability,
12 advantages that result through substantially greater simplicity of
design and construction. The
13 features of this novel combination are described as follows.
14
One feature is a one piece or unitary hollow body and cage with flow ports in
the integral
16 valve cage (disposed at the lower end of the plunger body) that can be
altered to control the flow
17 of fluid through the plunger on descent. During descent, the plunger
falls through the well and
18 any fluids therein. The fluids flow though the angled ports in the valve
cage and the hollow
19 body of the plunger. The ports in the cage may be oriented at different
angles, varied in number,
relieved, etc. to adjust the rate of descent. This unitary design minimizes
the number of parts and
21 the number of joints that must be formed and secured. One principle
benefit of the one-piece or
22 "unibody" construction is fewer parts to assemble and secure together,
and the elimination of
23 failures in the mechanisms used to secure the parts together.
24
The valve cage at the lower end and the end cap (if used) at the upper end are
mated to
26 the respective ends of the hollow plunger body with threaded joints and
secured with a crimp
27 ("crimple") formed in at least two equally spaced locations around the
hollow body. The crimple
28 functions as an inward-formed dent that effectively indents the wall of
the valve cage portion of
29 the hollow body into a corresponding relief machined into the external
threads of the (smaller)
11
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1 outside diameter of the retaining nut. The retaining nut (alternately
"end nut"), thus threadably
2 secured to the lower end of the valve cage, functions to close the open
end of the valve cage and
3 retain the poppet valve within the valve cage. The crimple feature
eliminates the need for
4 separate parts such as pins, screws, ball detents, lock nuts or washers,
etc, to lock a threaded joint
from loosening. The advantage of the crimple technique and mechanism is to
more reliably
6 prevent the inadvertent disassembly of the components secured to the
bypass plunger with screw
7 threads, thereby ensuring a true unibody bypass plunger that remains a
single unit throughout
8 many cycles of use. The term crimple is a contraction of the terms crimp
and dimple, to
9 characterize the crimp as approximating a crimp at a defined point as
compared with a
Circumferential crimp.
11
12 The outer surface of the hollow plunger body of the present invention
includes a series of
13 concentric rings or ridges machined into the outer surface of the hollow
body for approximately
14 one third the overall length of the hollow body at each end. The rings
or ridges thus provided act
as a seal to minimize the clearance between the plunger and the inside of the
well tubing through
16 which it descends and ascends. In the present invention, between these
two groups of concentric
17 rings, one group at each end of the hollow body, is a series of
concentric spiral (or helical)
18 grooves (not unlike the "valleys" of screw threads) machined into the
central portion of the outer
19 surface of the hollow body. The "central" portion may typically (but not
exclusively) be
approximately the central one-third of the length of the hollow body. The
pitch and profile of
21 these spiral grooves may be varied between a tight helix and an open
helix to vary the rate of
22 spin of the plunger as it descends and ascends. The purpose of spinning
the plunger is to prevent
23 flat spots from forming on the outside surface of the plunger, which
reduce the effectiveness and
24 the useful life of the bypass plunger. The cross section profile of the
grooves may also be varied
to facilitate the spin rate.
26
27 The "clutch" of one embodiment of the present invention consists of a
canted-coil garter
28 spring disposed within a circumferential groove inside the end nut. In
other words, no bobbin is
29 used, split or otherwise; just the canted coil spring that is disposed
within its groove and wrapped
12
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1 360 degrees around the stem of the valve dart. As used in the inventive
plunger, the coils of the
2 spring as formed are canted in the direction of its torroidal centerline
(i.e., a line passing through
3 the center of each coil of the spring) in a circumferential direction
around the stem diameter.
4 The coils of the canted coil spring, unlike a conventional coil spring in
which the coils are
disposed substantially at right angles to the centerline of the spring, are
disposed at an acute
6 angle relative to the centerline of the spring. This configuration allows
the spring to exert
7 tension at right angles to its centerline against the outside diameter
surface of the valve dart
8 stem. This property is enhanced when the outer diameter of the canted-
coil spring is constrained
9 by a cylindrical bore or in a groove surrounding the spring. The surface
of the valve dart stem in
one embodiment is preferably machined to a surface roughness of approximately
8 to 50
11 microinches, a standard specification for a very smooth finish. The
canted coil spring is supplied
12 in a 360 degree form with its ends welded together (thereby forming a
torroidal shape), enabling
13 it to be dimensioned to fit within a machined groove in the end or
retaining nut. Advantages of
14 this design include elimination of the bobbin components and greater
durability.
16 In the appended drawings, reference numbers that appear in more than
one figure refer to
17 the same structural feature. The drawings depict at least one example of
each embodiment or
18 aspect to illustrate the features of the present invention and are not
to be construed as limiting the
19 invention thereto. In addition, several alternative embodiments of a
clutch mechanism for a
plunger valve that utilizes canted-coil springs, and several alternative
embodiments of a plunger
21 valve dart having different valve stem profiles are included to suggest
the scope of modifications
22 that may be made to these components without departing from the concepts
employed in the
23 present invention. It should be understood that the term "plunger dart"
or simply "dart" may also
24 be named a poppet valve or a valve dart herein, all of which refer to
the same component.
26 Figure 1 illustrates a side exploded view of one embodiment of an
integrated, unibody
27 bypass plunger according to the present invention. The unibody bypass
plunger 10 is formed as
28 a single hollow plunger body 12 machined from a suitable material such
as a stainless steel alloy.
29 Such materials are well known in the art. Forming the hollow plunger
body as a single piece
13
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1 simplifies construction by reducing the number of parts to be connected
together with screw
2 threads, thereby reducing the opportunities for failure when a threaded
joint fails. Further, the
3 profiles of the flow ports in the cage 16, the sealing rings 22, 24, and
the centralized helix 24
4 may all be readily tailored during manufacture for a specific
application. The plunger body
includes the following defined sections: an ID fishing neck 14, an upper
section of sealing rings
6 22, an intermediate or central section of helical ridges or grooves 24, a
lower section of sealing
7 rings 26, and a valve cage 16 for enclosing and retaining a poppet valve
or valve dart 32. The
8 valve cage 16 includes a plurality of flow ports 18 disposed at typically
two to four equally-
spaced radial locations around the valve cage 16. In the illustrated
embodiment, two or more
crimples 20 to be described may be positioned as shown near the lower end of
the hollow body
ii 12 / cage 16 unit. The crimple 20 provides a mechanism to lock a
retaining nut or end nut 40
12 threaded on the open, lower end of the valve cage 16. The hollow body 12
may further include
13 wear grooves 30 disposed at selected ones of the sealing rings 22, 26 as
shown. Further,
14 disposed within the retaining or end nut 40 when the bypass plunger is
assembled is a canted-coil
spring 42 that functions as a clutch. This novel clutch design, which does not
require use of a
16 bobbin or similar structure, will be described herein below.
17
18 Continuing with Figure 1, the assembly of the bypass plunger 10
includes a valve dart 32
19 inserted head-end first through the valve cage 16 into the lower end of
the hollow body 12. The
valve head 36 and its sealing face 38 form a poppet valve head at the end of
stem 34. When
21 installed in the hollow body 12, the sealing face 38 of the poppet valve
or dart 32 is shaped to
22 contact a valve seat 48 machined into the internal bore 52 of the hollow
body 12 as shown in
23 Figure 4 that depicts the valve dart 32 in a closed position. The valve
dart 32 may be retained
24 within the valve cage 16 by the end nut 40 that may be installed in the
lower end of the valve
cage 16 and secured by screw threads 28 (See Figure 7). The end nut 40
includes in this
26 embodiment an external circular groove 44 around part of its threaded
portion. This groove 44
27 provides a relieved space so that a crimple 20 to be described may
extend into the groove 44 to
28 lock the external threads of the end nut 40 to corresponding internal
threads in the lower end of
29 the valve cage 16. The end nut 40 also preferably includes a canted-coil
spring 42 (to be
14
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1 described) disposed into an internal circumferential groove 50 (See
Figure 5). The canted-coil
2 spring 42 replaces a conventional clutch often used with dart-equipped
plungers and provides a
3 simpler and more effective structure to retard or brake the motion of the
valve stem as it moves
4 between open and closed positions.
6 Figure 2 illustrates a partial cross section view of the embodiment
of Figure 1 as
7 assembled to depict the relationship of several internal features of the
bypass plunger 10. The
8 valve dart 32, shown in its open position for descent, is confined within
the valve cage 16 by the
9 retaining nut 40. The canted-coil spring 42 surrounds the stem 34 of the
valve dart 32 to retard
its motion within the valve cage 16. The canted-coil spring 42 is retained
within the
11 circumferential groove 50 machined into the inner bore of the retaining
nut 40, as more clearly
12 shown in Figures 3 - 6. The inner bore 52 of the hollow body 12 includes
valve seat 48 and flow
13 ports 18 cut through the wall of the valve cage 16. One example of the
profiles of the sealing
14 rings 22, 26 and the helical grooves 24 are also depicted in Figure 2.
16 Figure 3 illustrates a cross section detail view of the lower (valve
cage 16) end of the
17 embodiment of the bypass plunger 10 shown in Figure 2 with the valve
dart 32 in an open
18 position. Figure 3 also depicts the use of a crimple 20 that deforms the
wall of the valve cage 16
19 so that an extended portion of the crimple 20 - the crimp 21, formed as
a dent in the outer surface
of the valve cage 16 - protrudes into a relieved portion 44 of the screw
threads of the retaining or
21 end nut 40. Persons skilled in the art will appreciate that the relieved
portion 44 may be
22 machined as a drilled hole of limited depth or a punched opening that
may be round, oval, or
23 rectangular in shape. In some cases, the formation of the crimple on the
outer surface of the
24 valve cage may extend into the threads of the retaining nut 40
sufficiently to prevent the
retaining nut from loosening.
26
27 The crimple 20 thus functions similar to a set screw or a pin to
prevent the loosening of
28 the screw threads. This feature is shown and described in greater detail
for Figures 7 and 8. In
29 the claims or in the description of the present invention, which
includes a one-piece or "unitary"
CA 02921179 2016-02-19
1
hollow plunger body and valve cage, the crimple feature may be variously
described and
2
understood as being disposed in the 'hollow body" or in the "valve cage"
portion of the hollow
3
body. Moreover, persons skilled in the art will recognize that the crimple
feature is a technique
4
that may be used in place of set screws, pins, etc., to secure threaded
components from turning
relative to each other. For example, end nuts at either end of a plunger body
or a bumper spring
6
or other similarly constructed device, may employ a crimple as described
herein to useful
7 advantage.
8
9
Figure 4, which is similar to Figure 3, illustrates a cross section detail
view of the lower
end of the embodiment of the valve cage (16) portion of the bypass plunger
shown in Figure 2
11
with the valve dart 32 in a closed or seated position, with the sealing
face 38 of the valve head 36
12
seated against the valve seat 48 inside the valve cage 16, and the
opposite end of the valve dart
13
32 slightly retracted - e.g., no more than about 0.030 inch - within the
end of the retaining nut 40.
14
Figure 5 illustrates a side cross section detail of the end (retaining) nut 40
and the canted-
16
coil spring 42 for use with the embodiment of Figures 1 - 4. In this
illustrated embodiment the
17
canted-coil spring 42 is disposed within a circumferential groove 50
inside the end nut 40. The
18
canted-coil spring 42 provides a clutch action on the stem 34 of the valve
dart 32 without using a
19
bobbin, split or otherwise. Only the canted-coil spring 42 that is
disposed within its groove 50
and wrapped 360 degrees around the stem 34 of the valve dart 32 acts to
restrain the motion of
21
the dart valve 32. As used in the illustrated bypass plunger 12, the coils
of the spring 42 as
22
formed are canted in the direction of its centerline, that is, in a
circumferential direction around
23 the stem 34 diameter.
24
The coils of the canted-coil spring, unlike a conventional coil spring in
which the coils
26
are disposed substantially at right angles to the centerline of the
spring, are disposed at an acute
27
angle relative to the centerline of the spring 42. This configuration
allows the canted coils of
28
spring 42 to exert tension radially inward at right angles to its
centerline against the outer surface
29
of the valve stem 34. The particular specifications of the canted-coil
spring, such as the material
16
CA 02921179 2016-02-19
1 used for the spring wire, its overall diameter, the diameter of the
coils, the acute angle the coils
2 form relative to the centerline of the spring, etc., may be selected to
suit the particular
3 dimensions of the bypass plunger, its expected environment, and other
conditions of use. The
4 performance of the canted-coil spring design is facilitated by the
surface finish provided on the
surface of the stem 34. Optimum performance is provided when the surface
finish, preferably
6 produced by machining, is held within the range of 8 to 50 microinches.
7
8 Advantages of this bobbinless, canted-coil spring design include at
least the following:
9 (a) reduction in the number of components required to provide the clutch
function; (b) the
canted-coil spring 42 is supported in a more confined space, reducing the
likelihood of failure
11 during hard impacts; (c) the need to assemble a split bobbin-with-garter
springs clutch is
12 eliminated - the canted-coil spring is simply inserted into its
circumferential groove 44; and (d)
13 the use of a conventional clutch bobbin assembly is eliminated. These
advantages arise from the
14 simplicity and the construction of the canted-coil spring.
16 Unlike a typical garter spring, which as supplied is simply a coil
spring that must be
17 formed into a circle and the ends typically crimped together (a hand-
assembly operation that is
18 prone to errors such as in cutting to length and crimping, etc.), the
canted-coil spring 42is
19 supplied to specification with the ends welded and the circular,
torroidal-form coil properly
dimensioned and configured for the particular application. Also unlike the
garter spring, the
21 canted-coil spring 42 need only be inserted into the circumferential
groove 50 in the end nut 40,
22 while the garter spring must be assembled onto the split bobbin; again a
more complex hand-
23 assembly operation. Thus the use of the canted-coil spring 42 ensures a
leaner manufacturing
24 process of a bypass plunger 10 that is substantially more reliable
because of the more durable
spring, and the more consistent tension it provides. These features markedly
improve the impact
26 resistance of the shifting mechanism (the valve cage 16, end nut 40, and
canted-coil spring 42) of
27 the unibody bypass plunger 10 disclosed herein.
28
17
CA 02921179 2016-02-19
1
Continuing with Figure 5, the surface of the stem 34 is preferably
machined and finished
2
to a surface roughness of approximately 8 to 50 microinches. The
combination of the radial
3
tension and the specified surface finish provides the appropriate amount
of friction to control the
4
motion of the valve dart 32 between the open and closed positions of the
stem 34 of the valve
dart 32. As noted above, the advantages of this design include elimination of
the bobbin
6 components and greater durability.
7
8
There are several alternate surface finishes to be illustrated and
described (See Figures 15
9
through 18) - combinations of recesses, grooves, undercuts, and surface
roughness - that may be
applied to the stem 34 of the valve dart 32 to limit or control the shifting
of the valve dart 32
11
during operation of the bypass plunger 10. These features can improve the
operation of the
12
bypass plunger under a variety of conditions while descending or ascending
in the well tubing.
13
For example, recesses such as snap ring grooves may be located at
strategic locations along the
14
stem 34 to prevent the stem 34 from sliding too easily within the canted-
coil spring 42 or restrain
the sliding when the bypass plunger encounters a condition that it might
otherwise interpret as
16 contacting the striker at the surface or the bumper spring at the bottom
of the well.
17
18
Figure 6 illustrates an end cross section detail of the end (retaining)
nut 40 and canted-
19
coil spring 42 surrounding the stem 34 of the valve dart 32 for use with
the embodiment of
Figures 1 - 4. As shown, the canted coil spring is supplied in a 360 degree
form that is
21 dimensioned to fit within the machined groove 50 in the end nut 40.
22
23
Figure 7 illustrates an enlarged version of Figure 3 to depict the form of
the crimple 20
24
used to lock the retaining or end nut 40 to the valve cage 16. The crimple
embodiment is an
effective technique for locking the threaded joint between the retaining or
end nut 40 and the
26
valve cage 16. This form of locking the joint also acts to prevent
loosening, thereby extending
27
the life of the joint. As shown, the crimple 20 is formed as a detent 20,
21 into the outer surface
28
of the valve cage 16. The dent or crimple 20 extends radially inward
through the threads 28 of
29
the retaining or end nut 40 and valve cage 16 and into the circumferential
recess 44 (shown in
18
CA 02921179 2016-02-19
3. cross section in Figure 7). The detent 20, 21 may be approximately
rectangular in cross section
2 to enable the narrower dimension to extend more readily into the recess
44.
3
4 Alternatively, the profile of the detent 20, 21 may be approximately
conical in form, as
though formed by a center punch having a conical point. In practice, the
crimple detent 20, 21
6 may be formed using a press as is well-known in the art. One preferred
example of a die used in
7 a press to form the crimple is illustrated in Figure 19 to be described.
The detent 20, 21 is
8 preferably placed in at least two locations, on opposite sides of the
valve cage 16 - i.e.,
9 approximately 180 degrees apart around the body of the valve cage 16 as
shown in Figure 8,
which illustrates an end cross section view of the embodiment depicted in
Figure 7.
11
12 Figure 9 illustrates a side view of a hollow body bypass plunger 60
according to the
13 present invention. The plunger of Figure 1 is depicted in Figure 9 with
a groove surrounding the
14 central portion of the body of the plunger and forming a tight helix
profile 62. Figure 10
illustrates a side view of a hollow body bypass plunger 70 according to the
present invention
16 having a more open helix profile 72 formed of several grooves, also
disposed in a central portion
17 24 of the plunger 70. The helical feature disposed in the central
portion 24 of the plungers 60, 70
18 may be called a centralized helix that is formed to cause the plunger to
rotate as it ascends and
19 descends or travels up and down through the well bore. Since the seal
provided by the sealing
rings 22, 26 is not total, fluids and gases escape past the sealing rings 22,
26. As the plunger 60,
21 70 passes through the well bore, the fluids and gases impart a torque to
the plunger 60, 70 by the
22 mechanism of the helical grooves 62, 72 respectively. The result is a
reduction in the occurrence
23 of flat spots along the outside diameter of the sealing rings 22, 26 of
the body of the plunger 60,
24 70 and consequent longer life.
26 The continuous helical groove machined into the central portion of
the hollow body
27 midway between the upper and lower ends thereof may have a predetermined
pitch, depth, and
28 profile. The variation in the pitch of the helical grooves 62, 72 as
shown in Figures 9 and 10
29 provides a means of varying the rate of spin imparted to the bypass
plungers 60, 70. In the
19
CA 02921179 2016-02-19
1 example of Figure 9, a single helical groove 62 encircles the body of the
plunger 60 from one up
2 to as many as eight times. Lengthening the fluid path around the plunger
60 tends to reduce the
3 spin rate of the plunger 60. In the example of Figure 10, a plurality of
helical grooves, typically
4 three or four (but could be from one to as many as twelve) spaced at
equal intervals around the
plunger body 60 provides a shorter fluid path around the plunger 70 to
increase the spin rate of
6 the plunger 70. In applications where the number of helical grooves is
greater than the typical
7 number of three to four, the width of the helical grooves may be
proportionately narrowed as the
8 number of grooves is increased.
9
It is important to note that the central helix 62, 72 is positioned mid-way
between the
11 sealing rings so as not to impair the sealing function of the sealing
rings 22, 26 yet still provide a
12 mechanism to cause the plunger 60, 70 to rotate during its up-and-down
travels. Moreover,
13 experience has shown that placing the helical grooves near the ends of
the plunger body 60, 70
14 causes the outside diameter of the plunger to wear faster, reducing the
profile depth and
effectiveness of the helical grooves and reducing the life of the bypass
plunger 60, 70.
16
17 The concept of the centralized helix may also be used with good effect
in sand plungers
18 used in sand-producing wells by improving the movement of the plunger
through sand-bearing
19 fluid because of the rotation imparted to the sand plunger. The rotation
may also tend to keep
the helical grooves - and the space between the plunger body and the well
tubing free of sand
21 build-up through the effects of centrifugal force.
22
23 One of the usual components of a dart or poppet valve as used in a
bypass or gas-lift
24 plunger is some form of clutch to restrain the motion of the dart,
thereby ensuring the efficient
operation of the dart in controlling the operation of the plunger. A
conventional split-bobbin
26 clutch may employ a circular bobbin split into two equal hemispherical
halves to enable
27 convenient assembly around the stem of the dart or poppet valve. The two
halves are generally
28 held against the stem by one or more (usually two) so-called "garter
springs" disposed in grooves
29 surrounding the bobbin assembly. Each bobbin half encircles the stem for
slightly less than a
CA 02921179 2016-02-19
1 full 180 degrees, so that the inside surface of each bobbin half may make
direct contact with the
2 stem of the dart under the tension provided by the garter spring(s). The
clutch assembly is
3 generally secured within the body of the plunger through which the dart
reciprocates during its
4 use. The clutch, through the friction exerted against the stem, acts to
damp the motion of the
stem within the bypass plunger so that it remains in the required closed or
opened position during
6 ascent or descent respectively through the well tubing.
7
8 Figures 11, 12, and 13 illustrate several alternative embodiments of
a split-bobbin clutch
9 assembly for use with darts (or dart valves or poppet valves) to restrain
the motion of the dart
and to support the dart in its closed and open positions within a bypass
plunger. These
11 embodiments differ from conventional clutches in the type of spring used
in place of a garter
12 spring and the location of the canted-coil spring on the bobbin
assembly. Conventional split
13 bobbin clutches typically use one or two ordinary coil springs that are
wrapped around the
14 bobbin assembly and its ends crimped together to form a circular loop
around the bobbin. The
spring tension of an ordinary coil spring, that acts like a rubber band around
the bobbin, exerts an
16 inward force to clamp the bobbin halves around the dart stem. In
contrast, the springs used in the
17 clutches illustrated in Figures 11, 12, and 13 have their coils canted
at an acute angle with the
18 centerline of the spring. That is, the coils of the spring all slant in
the same direction, and the
19 ends of the canted-coil spring are permanently secured together by
welding during the
manufacture of the canted-coil spring. The tension against the stem results
from the inherent
21 tension of the slanted (canted) coils, not from the tension in a coil
spring stretched around the
22 bobbin and stem. Thus, the spring merely needs to be looped over the
bobbin halves during
23 assembly. This results in uniform unit-to-unit clutch assemblies, which
translates to greater
24 dependability of the clutch performance under downhole conditions.
26 The split bobbins of Figures 11, 12, and 13 differ from one another
in the location of
27 grooves for supporting the canted-coil spring embodiment. Figure 11 has
the grooves positioned
28 in each side face of the bobbin halves as shown. Figure 12 depicts the
grooves formed in the
29 faces of the bobbin but intersecting the outer diameter of the bobbin so
that the grooves are
21
CA 02921179 2016-02-19
1 formed along the outer edges of the bobbin. Figure 13 shows a single
groove faulted around the
2 perimeter of the bobbin, with a canted-coil spring installed in the
groove. In this embodiment, a
3 bobbin could be constructed with more than one spring installed; thus
Figure 13 is provided here
4 to illustrate the concept.
6 It is possible to use a conventional coil spring in the embodiments
depicted in each
7 Figure 11, 12, and 13. However, several advantages are provided by the
use of a canted-coil
8 spring to hold the bobbin halves together. (1) The manufacturing process
of assembling the
9 bobbins is much simpler, involving substantially less hand work and
opportunity for errors in
assembly. (2) This configuration provides a more consistent tension because
the variation
11 between individual ones of the canted-coil springs can be held to a much
closer tolerance than
12 ordinary coil springs that must be individually assembled on the bobbin.
(3) The impact
13 resistance of the clutches assembled with canted-coil springs is greater
because the springs can
14 be specified with stronger spring constants, the ends are more securely
fastened, and the inward
tension exerted by the canted-coil configuration can be greater and more
closely controlled.
16 These advantages provide superior service life and reliability, and
lower operating costs,
17 especially important in downhole conditions characterized by high
impacts and corrosive
18 substances.
19
Figure 11 illustrates a first example of an alternative embodiment of a
plunger valve
21 clutch according to the present invention. The clutch 80 is assembled
from first 82 and second
22 84 halves of a split bobbin assembly 86. A first canted-coil spring 88
installed in groove 90, and
23 a second canted-coil spring 92 is installed in a similar groove 94 that
are visible in the cut-away
24 portion of the figure. When assembled on a valve stem the clutch 86
includes a gap 96 between
the first 82 and second 84 halves of the split bobbin assembly 86. The gap 96
ensures that the
26 tension exerted on the stem by the clutch 80 will be maintained.
27
28 Figure 12 illustrates a second example of an alternative embodiment
of a plunger valve
29 clutch according to the present invention. The clutch 98 is assembled
from first 92 and second
22
CA 02921179 2016-02-19
1 94 halves of a split bobbin assembly 104. A first canted-coil spring 106
is installed in groove
2 108, and a second canted-coil spring 110 is installed in a similar groove
112 that is not fully
3 visible in Figure 12 because it is installed on the opposite face of the
split bobbin assembly 104.
4 When assembled on a valve stem the clutch 98 includes a gap 114 between
the first 100 and
second 102 halves of the bobbin assembly 104. The gap 114 ensures that the
tension exerted on
6 the stem by the clutch 98 will be maintained.
7
8 Figure 13 illustrates a third example of an alternative embodiment of
a plunger valve
9 clutch according to the present invention. The clutch 116 is assembled
from first 118 and second
120 halves of a split bobbin assembly 122. A first canted-coil spring 124 is
installed in groove
11 126. If another canted-coil spring is desired, a second groove would be
required. When
12 assembled on a valve stem the clutch 116 includes a gap 128 between the
first 118 and second
13 120 halves of the spilt bobbin assembly 122. The gap 128 ensures that
the tension exerted on the
14 stem by the clutch 116 will be maintained.
16 It should be appreciated by persons skilled in the art that a single
canted-coil spring is
17 adequate for most applications because the spring can be manufactured
within a given size
18 constraint and spring-constant as assembled to exert the required inward
radial force and it is
19 thus not required to perform trial and error operations to select the
proper springs.
21 Figure 14 illustrates an alternate embodiment of the present
invention that is similar to
22 the embodiment of Figure 1 except Figure 14 is shown with a split bobbin
clutch instead of the
23 canted coil spring 42 as shown in Figure 1. The clutch, an assembly of
the split bobbin halves
24 140A, 140B is shown without a garter spring for clarity. The split
bobbins may be encircled by
one garter (or canted coil) spring as shown or two garter springs in the
manner of Figures 11, 12,
26 and 13. A partition nut 142, for retaining the bobbin assembly between
the retaining or end nut
27 40 and the partition nut 142, is shown adjacent to the clutch bobbins.
The partition nut 142 is
28 provided to ensure the clutch assembly 140A, 140B (and garter or canted
coil spring) remains in
29 position between the end nut 40 and the partition nut 142.
23
CA 02921179 2016-02-19
, 1
Figures 15 through 18 illustrate several embodiments of the valve
stem 34 portion of the
2
valve dart. These embodiments describe surface finishes or profiles
including several examples
3
of alternative surface profiles for moderating the reciprocating motion
of the valve stem within
4 the clutch structure of the unibody bypass plunger 10.
6
Figure 15 illustrates a first example of an alternate embodiment of a
plunger valve dart
7
150 according to the present invention. The valve dart 150 includes first
152 and second 154
8
grooves that encircle the stem 34 near each end of the stem 34. The
grooves in the illustrated
9
embodiment are formed as snap-ring grooves, a standard form for retaining
snap rings that is
easily produced during manufacture of the valve dart 150. In the illustrated
embodiment, the
11
snap-ring grooves, in cross section, may be folined as a 0.094 inch
radius (R.094,"or,
12
approximately 0.10") into the stem 34, to a depth of approximately 0.01
inch. For other
13
embodiments requiring other bypass plunger body diameters, these
dimensions may be varied or
14
scaled according to the dimensions of the bypass plunger and the canted-
coil spring to be used
with the bypass plunger. The first groove 152 provides a retention feature to
position the canted
16
coil spring 42 to retain the valve dart150 closed as the plunger ascends.
The first groove 152
17
acts to resist vibration effects that might tend to open the valve during
ascent. Such intermittent
18
opening and closing of the valve dart reduces the efficiency of the
plunger in lifting the fluids
19
and gas to the surface. Similarly, the second groove 154 acts to resist
vibration effects that might
tend to close the valve during descent. Such intermittent closing of the dart
valve 150 reduces
21
the speed of the plunger as it descends from the surface to the bottom of
the well to begin a new
22
lift cycle. The stem 34 is preferably machined to a surface roughness of
8 to 50 microinches as
23 in the embodiment shown in Figure 5.
24
Figure 16 illustrates a second example of an alternate embodiment of a plunger
dart valve
26
according to the present invention. The dart valve 160 includes first 162
and second 164 grooves
27
or recessed regions that encircle the stem 34 near each end of the stem
34. The first groove 162
28
in the illustrated embodiment is formed as a snap-ring groove, a standard
form for retaining snap
29
rings that is easily produced during manufacture of the dart valve 160.
The first groove 162 is
24
CA 02921179 2016-02-19
1 provided to enable the canted-coil spring to retain the dart valve 160 in
a closed position for
2 ascent of the plunger. The second groove or recessed region 164 at the
other end of the stem 34
3 near the valve head 36, is similar to the first groove or recessed region
162 except that it is
4 substantially wider along the length of the stem 34 to provide a
predetermined amount of
freedom for the dart valve to open even if it contacts the striker at the
surface with less than the
6 expected amount of upward-directed force. The longer intermediate length
166 of the stem 34 is
7 similarly recessed from the nominal stem diameter. This feature, by
allowing the valve dart 160
8 to gain momentum as it moves within the valve cage 16, facilitates the
movement of the stem 34
9 of the dart valve 160 through the restraining action of the canted-coil
spring 42 as the dart valve
moves between open and closed positions. The surface is preferably machined to
a surface
11 roughness of 8 to 50 microinches as in the embodiment shown in Figure 5.
12
13 Figure 17 illustrates a third example of an alternate embodiment of a
plunger dart valve
14 according to the present invention. In this embodiment of the dart valve
170, substantially the
entire length of the stem 34 includes a surface profile 172 formed of closely-
spaced alternating
16 ribs and grooves having a substantially unifouli profile - for instance
resembling a sinusoidal
17 wave in the illustrated example - as depicted in the detail view of
Figure 18 to be described. This
18 dart valve 170 is designed for use with the split bobbin clutch designs
illustrated in Figures 11,
19 12, and 13 described herein above.
21 Figure 18 illustrates a detail view of the profile of a feature of
the embodiment of Figure
22 16, wherein the alternating rib-and-groove profile is more clearly
shown. The surface profile
23 172 of the stem 34, shown in cross section in Figure 17 illustrates both
the ribs 174 and the
24 grooves 176 formed according to a radius R and separated by a spacing S.
The radius R may be
within the range of 0.020 inch to 0.150 inch and the spacing S between an
adjacent crest and
26 trough may be within the range of 0.020 inch to 0.075 inch. The values
of R on a particular
27 valve stem should be constant and the values of S on a particular valve
stem should be constant.
28
CA 02921179 2016-02-19
1
Figure 19 illustrates one example of a die for use in a press to form a
crimple used in the
2
embodiments of Figures 3, 4, 7, and 8. The body 200 of the die includes a
reduced diameter
3
shank 202 that is shaped at its end to form the crimple 20 in the outer
surface of the valve cage
4
16 portion of the unibody bypass plunger body 12. The crimple 20 is shown
in detail in Figures
3, 4 and 7, 8. The crimple 20, an indentation into the outer surface of the
valve cage 16, is
6
produced by the shape of the crimple blade 204. The crimple blade 204 as
shaped includes a
7
major radius 206, a minor radius 208, and a fillet radius 210. The major
radius 206 shapes the
8
blade 204 to the radius of the plunger body 12 at the location of the
crimple 20. The major
9
radius is formed to a radial dimension slightly larger than the body of
the plunger to be formed.
Thus, when the blade 204 contacts the plunger body and begins to form the
crimple 20, the
11
stresses produced in the metal body of the plunger tend to flow outward,
forming a smoother
12
crimple 20. Different plunger body diameters will, of course require
separate dies having the
13 appropriate major radius for the work piece.
14
The minor radius 208 is provided for a similar reason - to allow the stresses
of formation
16
to flow outward along the work piece. A small fillet radius 210 is
provided on the outside edges
17
of the blade 204 to reduce stress riser occurrence, a phenomenon well-
understood in the machine
18
arts. The operation of the press with the die 200 installed proceeds in a
slow, controlled manner,
19
after the work piece - the body 12 of the plunger - is supported in a
fixture or vise (the vise is not
shown, as it is not part of the invention and is well known to persons skilled
in the art) opposite
21
the die 200. This procedure achieves the desired crimp 21 into the recess
44 of the retaining nut
22
40. The curvatures of the major 206, minor 208, and fillet 210 radii,
besides reducing stresses in
23
the metal also retard the formation of cracks, both during manufacturing
and during use of the
24 bypass plungers in the field, where the plunger is subject to hard
impacts under some conditions.
26
Figure 20 illustrates an alternate embodiment to Figure 4, showing a split
bobbin clutch
27
assembly for a bypass plunger as disposed within a valve cage. The clutch
assembly is held in
28
place between the retaining or end nut 40 and a partition nut 142, both of
which are locked in
29
position by the use of a crimple 20. The crimple 20 deforms the wall of
the end nut 40 and the
26
CA 02921179 2016-02-19
1 valve cage 16, so that an extended portion of the crimples 20 - (same as
the crimp 21 shown in
2 Figures 3 and 4) - protrudes into a respective relieved portion 44 of the
screw threads of both the
3 retaining or end nut 40 and the partition nut 142. The crimple 20 thus
functions similar to a set
4 screw or a pin to prevent the loosening of the screw threads of the
retaining or end nut 40 and the
partition nut 142.
6
7 The valve dart 170, shown in Figure 20 in the valve closed (valve
seated as in Figure 4)
8 position within the valve cage 16, has the structure shown in Figure 17.
The surface profile 172
9 of the valve stem 34 portion of the valve dart 170 is depicted in Figure
18. The clutch bobbin
halves 140A and 140B are held against the stem 34 of the valve dart 170 by
springs 144 (which
11 could be canted-coil or conventional coil springs) that are installed in
the grooves 146 formed
12 into the circumference of the bobbin halves 140A and 140B. Note that,
when the valve dart 170
13 is seated inside the valve cage 16, the opposite end of the valve dart
170 slightly retracted - e.g.,
14 no more than about 0.030 inch - within the end of the retaining nut 40.
16 Returning to Figures 3 and 4, which depict the open and closed state
of the dart valves
17 within the valve cage, an alternate embodiment of the valve dart
assembly is depicted in Figures
18 21 and 22. The embodiments of Figures 3 and 4, and 21 and 22 illustrate
dart valves equipped
19 with the canted coil spring that functions as the clutch mechanism. The
alternate embodiment of
Figures 21 and 22 is preferred when the bypass plunger is used in downhole
environments where
21 sand is frequently suspended in the fluids being lifted to the surface.
It is preferred in this
22 alternate embodiment of the present invention to provide seals on either
side of the canted coil
23 spring to minimize the possibility for particles of sand to become
lodged in the coils of the
24 canted-coil spring, thereby reducing its effectiveness as a clutch
mechanism. The valve dart 232
within the valve cage 216 is shown in open and closed positions or states,
respectively Figures
26 21 and 22. Included in Figures 21 and 22 are first and second "slipper
seals" 244, 246, each one
27 installed in respective circumferential grooves 252, 254 formed in the
inside bore of the retaining
28 or end nut 240. The slipper seals 244, 246 are disposed on either side
of the canted-coil spring
29 242 installed in its circumferential groove 250 formed in the end nut
240. Like the canted coil
27
CA 02921179 2016-02-19
1 spring 242, the slipper seals 244, 246 surround the stem 234 of the valve
dart 232, thereby
2 forming a seal against sand or other types of particles becoming trapped
within the canted coil
3 spring 242.
4
The slipper seals 244, 246 may be formed from various ones of the PTFE
6 (polytetraflouroethylene) family of materials as 0-rings having a square
(or round) cross section.
7 Alternatives are filled Nylon such as oil-filled Nylon 6 and equivalents
Moly-filled Nylon 6,
8 solid lubricant-filled Nylon 6. Other alternatives include semi-
crystaline, high temperature
9 engineering plastics based on the PEEK (polyetheretherketone) or PAEK
(polyaryletherketone)
polymers.
11
12 While the invention has been shown in only one of its forms, it is
not thus limited but is
13 susceptible to various changes and modifications without departing from
the spirit thereof. For
14 example, canted-coil springs may be used to advantage in split bobbin
clutches as described
herein. Further, the profiles of the helical grooves and the flow ports in the
cage, the surface
16 finishes, the relative placements of the canted coil spring within the
retaining nut attached to the
17 cage, the form of the poppet valve - its stem, valve head, and the
corresponding valve seat in the
18 plunger body, the number of canted coil springs used within the
retaining nut or in a split bobbin
19 clutch assembly, the shape of the crimple and the die used to form it,
are some illustrative
examples of variations that fall within the scope of the invention. Moreover,
the crimple feature
21 is a technique that may be used in place of set screws, pins, etc., to
secure threaded components
22 from turning relative to each other. For example, end nuts at either end
of a plunger body or a
23 bumper spring or other similarly constructed device, may employ a
crimple as described herein
24 to useful advantage. The canted-coil spring used as a clutch may also be
used in other structures
for controlling sliding or reciprocating motion of a shaft within the bore of
a corresponding
26 structure of a device.
27
28 In regard to the use of a canted-coil spring in a clutchless
embodiment of a valve dart
29 assembly, several of the disclosed embodiments may use split bobbin
clutch assemblies in the
28
CA 02921179 2016-02-19
. 1 claimed combinations, wherein canted -coil springs or conventional
coil springs may be used to
2 hold the bobbin halves together around the stem of the valve dart,
without departing from the
3 concepts of the invention as disclosed herein.
4
A final note about the drawings: detail features shown in the drawings may be
enlarged to
6 more clearly depict the feature. Thus, several of the drawings are not
precisely to scale.
7
29
